The present invention relates generally to polishing pads and methods of producing the same.
Polishing pads for removing scratches from surfaces of polished glass and other objects are known. They are used on polishing machine tools for repair-polishing of front surfaces of airplane windows, etc. Some of such pads are disclosed in U.S. Pat. Nos. 4,969,914 and 4,709,513. Known polishing pads of this type which are identified as xe2x80x9chydropadsxe2x80x9d include a working layer, a body which supports the working layer, a xe2x80x9cVELCROxe2x80x9d-type connecting layer for connecting the pad to a power tool, and a connection layer for connecting the body to the xe2x80x9cVELCROxe2x80x9d-type connecting layer. The working layer of the pads is a polishing powder, for example CeO2, with the particle size 1.5-5 xcexcm, which are fixed by adhesive on the body. The body is formed as a non-knitted substrate which is covered by an adhesive suspension, on which polishing powder, for example CeO2 is placed. Such a pad is shown in FIG. 1, wherein reference numeral 1 identifies a working layer including an adhesive 2 and a polishing powder with polishing grains 3 embedded in the adhesive 2, a body identified with reference numeral 4 and composed of a non-knitted material, a xe2x80x9cVELCROxe2x80x9d-type layer including a carrier 5 and a plurality of projections formed for example as loops 7, and a connection layer 6 composed of a pressure sensitive adhesive. During the manufacture of the pad, the adhesive 2 of the working layer 1 s hardened and fixed with the grains 3 of the polishing powder on the surface of the body 4.
The above mentioned polishing pad has several disadvantages. The very small grains of the polishing powder with the size 1.5-5 micron located on the adhesive suspension must penetrate into the interior of the adhesive. However, the small size of the grains and their small weight as well as their relatively great surface and a viscosity of the adhesive suspension prevent a deep penetration of the grains into the adhesive suspension. The polishing grains 3 are fixed in the adhesive suspension only over 25-35% of their height. This is a reason for a low working ability and a minimal service life of the tool pad. During the operation of the pad, as a result of the displacement, pressure and temperature, the pressure sensitive adhesive of the connecting layer 6 looses its viscosity and the pad breaks apart, or in other words, the body 4 with the working layer 1 is separated from the xe2x80x9cVELCRO-type layer 5-6.
Accordingly, it is an object of present invention to provide a polishing pad of the above mentioned general type which avoids the disadvantages of the prior art.
It is also an object of the present invention to provide a method of producing the polishing pad, which makes possible making of a polishing pad which eliminates the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a polishing pad which has a working layer provided with a plurality of polishing grains; an attachment layer for attaching the pad to a power tool; and a connection layer located between said working layer and said attaching layer and composed of a vulcanizable polymeric material, such that when the working layer is applied on the attaching layer with heat and pressure, the connection layer is vulcanized and immovably connects the working layer to the attaching layer.
In accordance with another feature of the present invention a method of producing of a polishing pad is proposed, which includes the steps of providing a working layer with a plurality of polishing grains; providing an attachment layer for attaching the pad to a power tool; and connecting the working layer with the attaching layer by providing a vulcanizable polymeric layer between them and applying a temperature and pressure sufficient for vulcanization of the connection layer so as to connect the working layer with the attaching layer by the connection layer.
When the pad is designed and the method is performed in accordance with the present invention then a polishing pad is produced which avoids the disadvantages of the prior art and provides a high working ability and a long service life.
In accordance with another feature of the present invention, the temperature and pressure is applied simultaneously to the pad assembled of all above mentioned layers, so that simultaneously with vulcanization of the connection layer and connection of the working layer with the attaching layer, the polishing grains are forcedly moved by the applied pressure into the interior of an adhesive suspension of the working layer. As a result the grains are introduced deeply into the working layer so that hundred percents of their height is inside the working layer.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.